Method for filling ballast tanks



United States Patent Inventor Charles F. Myers, Jr.

Bel Air, Maryland Appl. No, 800,288

Filed Feb. 18, 1969 Patented Dec. 1, 1970 Assignee Harry T. Campbell Sons Corporation Towson, Maryland a corporation of Maryland METHOD FOR FILLING BALLAST TANKS 5 Claims, No Drawings 3,363,806 1/1968 Blakeslee etal.

ABSTRACT: A method for filling a ballast tank or space of a vessel with a flowable inert inorganic ballast composition comprising water and a mixture of graded aggregate and noncementitious filler, said filler being present in amounts of about 530 weight percent of said mixture, said aggregate and filler having a specific gravity ranging between about 2.40-2.90, said aggregate and filler being graded to provide a mixture having minimum percent voids so that when said mixture is combined with water in amounts of 6-25 percent by weight of the total ballast composition, said ballast composition has a density ranging between about 115-l60 pounds per cubic foot, the steps of introducing said ballast composition into said ballast tank or space and vibrating said tank or other structure defining said space at a frequency of at least about 1000 vibrations per minute.

1 METHOD FORFILLING BALLAST TANKS This invention relates to the ballasting of ships and more particularly to filling a ballast tank or space of a vessel with an inert, inorganic ballast composition of controlled particle size distribution and of exceptionally high density.

Heretofore, it has been a common practice to employ sea water as a ballast for ships although such practice creates certain disadvantages, not the least of which is a severe corrosion problem. Additionally, the use of sea water because of its proximity in density to fresh water, finds relatively little effective application in situations where the ballast is required to lower the center ofsgravity, to the desired degree, of cargo ships destined for use in the transportation of low density cargo, such as containerized freight, a portion of which is often stacked above the deck of the cargo ship. V

Efforts to overcome the disadvantages attendant with the use of sea water as a ballast agent, have resulted in the utilization of a solid ballast material such as dense concrete slabs and pig iron. While such solid ballast material can eliminate this density problem, its widespread use has been discouraged because of its difficulty to be conveniently placed or removed in the ship, thereby often necessitating its placement in areas which would otherwise be considered as valuable cargo space.

More recent efforts have returned to the concept of utilizing a liquid ballast material of high density which would alleviate the problem of introducing and removing the same from conventional ballast tanks or space in cargo ships, yet provide alteration of the center of gravity of cargo ships to the extent desired.

Representative of such liquid ballast material is one prepared from a high density inorganic material such as barite which requires relatively large amounts of water in order to achieve the required final density of the ballast composition. This large water requirement is considered disadvantageous in several respects. For instance, the incorporation of large amounts of water in the ballast composition gives rise to a sloshing effect within the ballast space during movement of the vessel which effect is not desirable. Further because the ballast composition essentially retains its liquid characteristics when in place, there is a danger that in the event of damage to the ballast tanks or space, a significant portion, if not all of the ballast composition, will be lost. Moreover, repair of ballast tanks or space is often rendered cumbersome with the presence of a liquid ballast material therein and generally before such repairs can be made, the liquid ballast composition has to be removed.

lthas also been observed that such liquid ballast materials often are contaminated with or contain organic materials. in order to prevent the formation of explosive gases when such contaminated liquid ballast materials are in place, it has been found necessary to admix therewith expensive bacteriostatic agents. Additionally, because of therelatively high water content of these liquid ballast materials, generally in the order of about 25-30 percent, the corrosive nature thereof is accentuated and to alleviate this problem it has been found necessary not only to include corrosion inhibitors but also, in many instances, to pretreat the space which receives these liquid ballast materials by coating the same with a corrosion inhibiting composition. Obviously, the cost of these additives and coating measures decrease significantly the economic attractive. ness of the use of these known liquid ballast compositions with respect to their case of placement and removal from the ballast area of cargo ships.

it has recently been found that the disadvantages associated or experienced with the use of such liquid ballast materials can be overcome by utilizing a flowable, inert, inorganic ballast composition prepared from a mixture of graded, normal density aggregate materials and a nonccmentitlous filler. Surprisingly, it has been found that the use of normal density aggregate and filler as opposed to the use of high density inorganic materials requires less water in admixture therewith to attain comparable ballast composition density values.

Conventionally established requlrements or specifications for a fluid ballast material include the following considerations. The'fluid should not promote the formation of aerobic or anaerobic bacteria and must therefore, if it contains or becomes contaminated with organic materials, be provided with a bacteriostatic agent. The fluid also must be anticorrosive and should therefore be alkaline in nature. While corrosion inhibitors can be added to achieve anticorrosivity, such inhibitors should not deleteriously affect the action of the bacteriostatic agent or affect the physical properties of the fluid such as its pumpability or the like. if solids are employed in the fluid composition. the fluid should have sufficient viscosity and gel characteristics to minimize settling of solids. Additionally, the thermal expansion characteristics of the fluid should be such that its volumetric expansion should not be greater than 0.4 percent over a temperature range from 32 F. to F. and should be capable of withstanding an ambient temperature of 32 F. without freezing.

The above referred to recently developed novel ballast system meets substantially all these requirements and as pointed out above overcomes the disadvantages experienced in the use of liquid ballast systems prepared from high density inorganic materials combined with relatively large amounts of water. This new ballast material utilizes in admixture with water an inert, inorganic material of controlled particle size distribution having normal density characteris ics and which material when so admixed with relatively minor amounts of water imparts to the ballast composition an exceptionally high density.

The inert, inorganic material component of the ballast composition of this invention comprises a mixture of graded aggregate and none noncementitious filler, the filler being present in amounts of about 5-30 weight percent of the mixture. The aggregate and filler are characterized as exhibiting normal density properties, i.e. the specific gravity thereof ranges between about 2.40 to about 2.90. it is also essential that the aggregate and filler be graded, i.e. have a controlled particle size distribution, to provide a mixture having minimum percent voids so that when the mixture is combined with water in amounts of 6-25 percent by weight of the total ballast composition, the ballast composition has a density ranging between about to about l60 pounds per cubic foot: The novel ballast composition used in this invention is generally alkaline by nature rather than acidic and does therefore exhibit favorable anticoriosive characteristics although it will be recognized that if desired enhanced anticorrosive properties can'be attained by the inclusion therein of conventional corrosion inhibitors or the implementation of conventional anticorrosion measures. This novel ballast composition is capable of being pumped by concrete pumps and since it contains relatively little water, essentially little or insignificant settling occurs. Further, because the ballast composition contains only minor amounts of water, it does not, when in place, produce or occasion a sloshing phenomenon. To the contrary after placement in the ballast space, the hydraulic properties imparted thereto during placement essentially disappear and the ballast composition assumes the characteristics of an essentially nonflowable, nonhydraulic material which can, neverthelessbe removed by a simple water flushing operation using astream of water under conventional pressures ranging from about 40-100 pounds per square inch. This characteristic, of course, permits removal of the ballast composition from selective areas within the total ballast space and substantially eliminates any concern of loss or outflow of the entire or substantial amounts of the ballast composition in the event of damage to the ballast tank or space, which loss or outflow is a definite possibility when a ballast composition retains essentially its liquid characteristics when in place. Further, the thermal expansion properties of the ballast material of this invention meet recognized standards and the volumetric expansion characteristics thereof are in the order of about 0.1 percent. As indicated above, the density of this novel ballast material ranges between about l 15- pounds per cubic foot.

The aggregate component of the ballast composition used in this invention can be any commercially available inert, inorganic noncementitious material such as quartz, quartzite, gravel, granite, trap rock, limestone and the like. The filler component can be of the same chemical composition as the aggregate component. Representative filler materials include limestone from dust collectors, silica flour, slag fines including glass furnace slag fines, boiler slag fines, fines from wet scrubbers, fly ash or dust from dust collectors. It is essential that the filler be inert, inorganic and noncementitious.

As indicated above the aggregate and filler, having a specific gravity ranging between about 2.40 to about 2.90, are graded to provide a mixture having minimum percent voids so that when the mixture is combined with water in amounts of about 6-25 percent by weight of the total ballast composition, the ballast composition has a density of about 1 ll60 pounds per cubic foot. The percent or fraction of any given particle size of said aggregate and filler, will of course be dependent on a number of easily ascertainable factors such as the maximum size of particle to be included in the mixture, the apparent specific gravity of the aggregate and filler chosen within the above stated range, and the density of the ballast composition desired also within the above stated range. It has been found convenient to utilize commercially available aggregate and filler which initially substantially pass through a 1- inch screen and which are graded to provide fractions of specific sizes, which fractions when mixed together and combined with definite but relatively minor proportions of water yield a ballast composition having a density ranging from about 1 l5l60 pounds per cubic foot. Other convenient ballast compositions useable in accordance with this invention can be prepared from graded aggregate and filler initially substantially passing through three-eighths inch, No. 4 and No. 8 US. sieves.

The following examples illustrate the gradation of various aggregate and noncementitious filler materials in accordance with sieve analysis (percent passing) thereof based on essentially the maximum particle size desired in the total ballast composition.

Percent III Example I The following examples illustrate the use of graded aggregate and filler to produce the ballast composition of the present invention.

Example VII VIII IX (a) Aggregate and tiller sieve analysis percent (pm n; (b) Limestone (wt.percent dry basis).. 100 100 (c) Silica sand (wt. percent dry basis) 0 0 38. 25 (d) Quartzite gravel (wt. percent dry basis). 0 0 46. 75 (e) Apiparent specific ravity (ASTM C128) 2. 82 2.82 2.67 (I) 80 d density (lbs. It!) 176. l 176. l 166. 7 (g) Dry compacted unit weight (lb 127. 4 130.0 133.8 (h) Percent voids, based on (g.) X100 27. 7 26. 2 1i). 7 (1) Percent water by weight of dry aggregate to produce fluid mix i4. 0 13. 7 1.00 (1) Density of ballast ASTM C-138 130 136 144 I Same as Example II.

I Same as Example III.

8 Sonic as Example IV.

When employing a mixture of aggregate and noncementitious filler, as in Examples Vll-lX wherein the maximum particle size is essentially less than three-eighths inch, the aggregate preferably has the following sieve analysis (percent passing): %-99 to 100 percent; 04-50 to 60 percent; 08-39 to 49 percent; 016-35 to 45 percent; 030-27 to 37 percent; 050-10 to 16 percent; 0100-1 to 2 percent. The filler material which is present in amount of about 15 weight percent of the total dry mixture has a sieve analysis (percent passing): OlOO-about percent to about percent; 0200-about 80 percent to about 100 percent and 0325-about 40 percent to about 100 percent. The specific gravity of the aggregate and filler is 2.64 and when combined with 12.5 percent water based on the total weight of the composition, the ballast composition has a density of about pounds per cubic foot.

The following Examples also illustrate the use of mixtures of aggregate and noncementitious fillers, essentially the same as those described in Examples 1, V and Vi as suitable for use in ballasting cargo vessels in accordance with the present invention.

Example X XI XII (a) Aggregate and filler sieve analysis (percent P g (b) Limestone (wt. percent dry basis), percent. 8 17 25 (e) Silica sand (wt. percent dry basis), percent. 40 83 75 (d) Quartzite gravel (wt. percent dry basis),

percent 52 O 0 (e) Apparent s eeific gravity (ASTM C-128). 2. 64 2. 66 2. 67 (1') Sol (1 dens ty (lbs./it. 164. 8 166. 1 166. 7 (g) Percent water by weig t of dry mixture to produce ballast composition 7. 4 18. 0 25. 0 (h) Density of ballast composition 147. 0 132. 6 125. 0

1 Same as Example I. 2 Same as Example V. 3 Same as Example VI.

Any of the above mixtures of graded aggregate and filler can be combined with water in amounts sufficient to produce a ballast composition having a density ranging between about ll5l60 lbs./ft. in accordance with the following relationship:

wherein D is the density of the ballast composition within the above stated limits; p,,, is the apparent specific gravity of the graded mixture of aggregate and filler ranging between 2.40- 2.90 and P is the weight percent of water based on the total weight of the ballast composition.

The ballast compositions useful in this invention are employed in cargo ships to lower the center of gravity thereof, especially when containerized freight is transported on such ships. The ballast compositions can be prepared by admixing the mixture of aggregate and filler with water in any conventional mixing apparatus such as a mix concrete truck or the like. in addition to delivering the ballast material by means of a suitable concrete pump and associated piping to the ballast tank or space, the ballast composition can also be delivered thereto by other conventional means such as belt conveyors, chutes or the like.

in accordance with the procedures of the present invention, the above defined ballast composition is introduced into a ballast tank or other structure defining the ballast space, which tank or structure is vibrated sufficiently to impart hydraulic properties to the ballast composition, i.e. render the same flowable, whereby the ballast composition fills the tank or structure to the depth desired.

The space to be filled. with the ballast composition of the present invention preferably is defined by the false bottom and actual bottom of a double-bottomedcargo vessel suitable for use in transporting containerized low density freight.

The ballast tank or structure is vibrated generally at a frequency of at least about 1000 vibrations per minute and up to about 8000 vibrations per minute. Preferably, the frequency is about 3000-4000 vibrations per minute. Any convenient means for vibrating the ballast tank or structure can be employed such as pneumatic or electrical vibrators, the latter being preferred. It is important to apply the vibrational force indirectly to the ballast composition, rather than directly, by vibrating the structure defining the ballast space as opposed to inserting the source of vibrational energy directly into the ballast composition.

Surprisingly, it has been found that the above ballast composition, treated in accordance with the present invention, which prior to said treatment lacks any significantly discernible hydraulic characteristics, assumes hydraulic characteristics to a degree sufficient to render the same flowable as a liquid thereby permitting it to fillvthe ballast space to any depth desired. This phenomenon was especially surprising since it was observed that the application of even reasonably high pressures to the ballast composition failed to impart thereto the flowable characteristics achieved by the present invention, but rather caused densification of the mass.

lclaim:

l. A method for filling a ballast tank or space of a vessel,

water and a mixture. of graded aggregate and noncementitious filler, said filler being present in amounts of about 5-30 weight percent of said mixture, said aggregate and filler having a specific gravity ranging between about 2.402.90, said aggregate and filler being graded to provide a mixture having minimum percent voids so that when said mixture is combined with water in amounts of 6--25 percent by weight of the total ballast composition. said ballast composition has a density ranging between about 115 -160 pounds per cubic foot. the steps comprising introducing into a ballast tank or other structure defining said ballast-space said ballast composition and vibrating said tank or structure sufficiently to impart hydraulic properties to said ballast composition whereby said ballast composition fills said tank or structure to the depth required.

2. The method of claim 1 wherein said tank or structure is vibrated at a frequency of at least about 1000 vibrations per minute.

3. The method of claim 1 wherein said tank or structure is vibrated at a frequency ranging from about l000-8000 vibra tions per minute.

4. The method of claim 3 wherein said tank or structure is vibrated at a frequency ranging from about 3000-4000 vibrations per minute.

5. The method of claim 1 wherein said vessel is a doublebottomed vessel and said ballast composition is introduced into the space between the false bottom and actual bottom thereof. 

